Generally speaking, the present invention is directed to a method of providing good starting characteristics in a synchronous motor which includes inter-meshed stator poles and a permanent magnet rotor with rotor poles rotating within the inter-meshed stator poles and wherein a field coil which generates flux to cause rotation of the rotor is disposed adjacent the inter-meshed stator poles in a side-by-side relationship, the method comprising, providing shading means for a predetermined number of stator poles to provide a group of shaded poles and a group of unshaded poles, selecting a reference pole from each of the groups, determining the flux phase difference between the reference pole and individual poles of a group, and converting the phase difference to a mechanical angle and locating the individual poles with respect to each other according to the mechanical angle for an individual pole.
The present invention relates to synchronous motors and more particularly to a synchronous motor wherein a field coil is disposed adjacent to the rotor and stator assembly in a side-by-side relationship.
There are a multitude of applications for synchronous motors of the type having a permanent magnet rotor. Many of these applications are in timing devices such as clocks, and in appliances such as washers and dryers which utilize time sequence switches. Various space requirements in these applications sometimes makes it very difficult to provide adequate space for the synchronous motor. For example, in some applications the space requirements dictate that the field coil, which energizes the motor, be positioned adjacent to the rotor and stator assembly in a side-by-side relationship. Such relationship provides a motor which is flatter than that of a synchronous motor wherein the field coil and the rotor and stator assembly are in axial alignment.
It has been found that when using a side-by-side relationship of the field coil and the rotor and stator assembly that flux phase differences cause the motor to have poor starting characteristics.